1. LIGO-G010398-00-M Catching the Waves with LIGO Barry Barish 26 Sept 01

2. LIGO-G010398-00-M Sir Isaac Newton  Perhaps the most important scientist of all time!  Invented the scientific method in Principia  Greatest scientific achievement: Universal Gravitation

3. LIGO-G010398-00-M Newton Universal Gravitation  Three laws of motion and law of gravitation (centripetal force) disparate phenomena »eccentric orbits of comets »cause of tides and their variations »the precession of the earth’s axis »the perturbation of the motion of the moon by gravity of the sun  Solved most known problems of astronomy and terrestrial physics »Work of Galileo, Copernicus and Kepler unified.

4. LIGO-G010398-00-M Einstein’s Theory of Gravitation Newton’s Theory “instantaneous action at a distance” Einstein’s Theory information carried by gravitational radiation at the speed of light

5. LIGO-G010398-00-M General Relativity the essential idea  Overthrew the 19 th -century concepts of absolute space and time  Einstein: gravity is not a force, but a property of space & time »Spacetime = 3 spatial dimensions + time »Perception of space or time is relative  Concentrations of mass or energy distort (warp) spacetime  Objects follow the shortest path through this warped spacetime; path is the same for all objects

6. LIGO-G010398-00-M General Relativity Einstein theorized that smaller masses travel toward larger masses, not because they are "attracted" by a mysterious force, but because the smaller objects travel through space that is warped by the larger object  Imagine space as a stretched rubber sheet.  A mass on the surface will cause a deformation.  Another mass dropped onto the sheet will roll toward that mass.

7. LIGO-G010398-00-M Einstein’s Theory of Gravitation experimental tests Mercury’s orbit perihelion shifts forward an extra +43”/century compared to Newton’s theory Mercury's elliptical path around the Sun shifts slightly with each orbit such that its closest point to the Sun (or "perihelion") shifts forward with each pass. Astronomers had been aware for two centuries of a small flaw in the orbit, as predicted by Newton's laws. Einstein's predictions exactly matched the observation.

8. LIGO-G010398-00-M New Wrinkle on Equivalence bending of light  Not only the path of matter, but even the path of light is affected by gravity from massive objects First observed during the solar eclipse of 1919 by Sir Arthur Eddington, when the Sun was silhouetted against the Hyades star cluster Their measurements showed that the light from these stars was bent as it grazed the Sun, by the exact amount of Einstein's predictions. Einstein Cross Photo credit: NASA and ESA A massive object shifts apparent position of a star The light never changes course, but merely follows the curvature of space. Astronomers now refer to this displacement of light as gravitational lensing.

9. LIGO-G010398-00-M Einstein’s Theory of Gravitation experimental tests “Einstein Cross” The bending of light rays gravitational lensing Quasar image appears around the central glow formed by nearby galaxy. The Einstein Cross is only visible in southern hemisphere. In modern astronomy, such gravitational lensing images are used to detect a ‘dark matter’ body as the central object

10. LIGO-G010398-00-M Einstein’s Theory of Gravitation gravitational waves a necessary consequence of Special Relativity with its finite speed for information transfer time dependent gravitational fields come from the acceleration of masses and propagate away from their sources as a space- time warpage at the speed of light gravitational radiation binary inspiral of compact objects

11. LIGO-G010398-00-M Einstein’s Theory of Gravitation gravitational waves Using Minkowski metric, the information about space-time curvature is contained in the metric as an added term, h . In the weak field limit, the equation can be described with linear equations. If the choice of gauge is the transverse traceless gauge the formulation becomes a familiar wave equation The strain h  takes the form of a plane wave propagating at the speed of light (c). Since gravity is spin 2, the waves have two components, but rotated by 45 0 instead of 90 0 from each other.

12. LIGO-G010398-00-M Gravitational Waves the evidence Neutron Binary System PSR 1913 + 16 -- Timing of pulsars   17 / sec ~ 8 hr Neutron Binary System separated by 106 miles m 1 = 1.4m  ; m 2 = 1.36m  ;  = 0.617 Prediction from general relativity spiral in by 3 mm/orbit rate of change orbital period

13. LIGO-G010398-00-M Hulse and Taylor results  due to loss of orbital energy  period speeds up 25 sec from 1975-98  measured to ~50 msec accuracy  deviation grows quadratically with time emission of gravitational waves

14. LIGO-G010398-00-M Radiation of Gravitational Waves from binary inspiral system LISA Waves propagates at the speed of light Two polarizations at 45 deg (spin 2)

15. LIGO-G010398-00-M Interferometers space The Laser Interferometer Space Antenna (LISA) The center of the triangle formation will be in the ecliptic plane 1 AU from the Sun and 20 degrees behind the Earth.

16. LIGO-G010398-00-M Astrophysics Sources frequency range  EM waves are studied over ~20 orders of magnitude »(ULF radio  HE  -rays)  Gravitational Waves over ~10 orders of magnitude » (terrestrial + space) Audio band

17. LIGO-G010398-00-M Suspended mass Michelson-type interferometers on earth’s surface detect distant astrophysical sources International network (LIGO, Virgo, GEO, TAMA) enable locating sources and decomposing polarization of gravitational waves. Interferometers terrestrial

18. LIGO-G010398-00-M Laser Beam Splitter End Mirror Screen Viewing Michelson Interferometer

19. LIGO-G010398-00-M Recycling Mirror Optical Cavity 4 km or 2-1/2 miles Beam Splitter Laser Photodetector Fabry-Perot-Michelson with Power Recycling Suspended Test Masses

20. LIGO-G010398-00-M Sensing a Gravitational Wave Laser signal Gravitational wave changes arm lengths and amount of light in signal Change in arm length is 10 -18 meters

21. LIGO-G010398-00-M How Small is 10 -18 Meter? Wavelength of light, about 1 micron One meter, about 40 inches Human hair, about 100 microns LIGO sensitivity, 10 -18 meter Nuclear diameter, 10 -15 meter Atomic diameter, 10 -10 meter

22. LIGO-G010398-00-M What Limits Sensitivity of Interferometers? Seismic noise & vibration limit at low frequencies Atomic vibrations (Thermal Noise) inside components limit at mid frequencies Quantum nature of light (Shot Noise) limits at high frequencies Myriad details of the lasers, electronics, etc., can make problems above these levels

23. LIGO-G010398-00-M Noise Floor 40 m prototype displacement sensitivity in 40 m prototype. comparison to predicted contributions from various noise sources sensitivity demonstration

24. LIGO-G010398-00-M Phase Noise splitting the fringe spectral sensitivity of MIT phase noise interferometer above 500 Hz shot noise limited near LIGO I goal additional features are from 60 Hz powerline harmonics, wire resonances (600 Hz), mount resonances, etc expected signal  10 -10 radians phase shift demonstration experiment

25. LIGO-G010398-00-M LIGO astrophysical sources LIGO I (2002-2005) LIGO II (2007- ) Advanced LIGO

26. LIGO-G010398-00-M Interferometers international network LIGO Simultaneously detect signal (within msec) detection confidence locate the sources decompose the polarization of gravitational waves GEO Virgo TAMA AIGO

27. LIGO-G010398-00-M LIGO Sites Hanford Observatory Livingston Observatory

28. LIGO-G010398-00-M LIGO Livingston Observatory

29. LIGO-G010398-00-M LIGO Hanford Observatory

30. LIGO-G010398-00-M LIGO Plans schedule 1996Construction Underway (mostly civil) 1997Facility Construction (vacuum system) 1998Interferometer Construction (complete facilities) 1999Construction Complete (interferometers in vacuum) 2000Detector Installation (commissioning subsystems) 2001 Commission Interferometers (first coincidences) 2002Sensitivity studies (initiate LIGOI Science Run) 2003+ LIGO I data run (one year integrated data at h ~ 10 -21 ) 2006Begin LIGO II installation

31. LIGO-G010398-00-M LIGO Facilities beam tube enclosure minimal enclosure reinforced concrete no services

32. LIGO-G010398-00-M LIGO beam tube  LIGO beam tube under construction in January 1998  65 ft spiral welded sections  girth welded in portable clean room in the field 1.2 m diameter - 3mm stainless 50 km of weld NO LEAKS !!

33. LIGO-G010398-00-M LIGO I the noise floor  Interferometry is limited by three fundamental noise sources  seismic noise at the lowest frequencies  thermal noise at intermediate frequencies  shot noise at high frequencies  Many other noise sources lurk underneath and must be controlled as the instrument is improved

34. LIGO-G010398-00-M Beam Tube bakeout I = 2000 amps for ~ 1 week no leaks !! final vacuum at level where not limiting noise, even for future detectors

35. LIGO-G010398-00-M LIGO vacuum equipment

36. LIGO-G010398-00-M Vacuum Chambers vibration isolation systems »Reduce in-band seismic motion by 4 - 6 orders of magnitude »Compensate for microseism at 0.15 Hz by a factor of ten »Compensate (partially) for Earth tides

37. LIGO-G010398-00-M Seismic Isolation springs and masses damped spring cross section

38. LIGO-G010398-00-M Seismic Isolation suspension system support structure is welded tubular stainless steel suspension wire is 0.31 mm diameter steel music wire fundamental violin mode frequency of 340 Hz suspension assembly for a core optic

39. LIGO-G010398-00-M LIGO Noise Curves modeled wire resonances

40. LIGO-G010398-00-M Core Optics fused silica Caltech data CSIRO data  Surface uniformity < 1 nm rms  Scatter < 50 ppm  Absorption < 2 ppm  ROC matched < 3%  Internal mode Q’s > 2 x 10 6

41. LIGO-G010398-00-M Core Optics installation and alignment

42. LIGO-G010398-00-M LIGO laser  Nd:YAG  1.064  m  Output power > 8W in TEM00 mode

43. LIGO-G010398-00-M Commissioning configurations  Mode cleaner and Pre-Stabilized Laser  2km one-arm cavity  short Michelson interferometer studies  Lock entire Michelson Fabry-Perot interferometer “First Lock”

44. LIGO-G010398-00-M Why is Locking Difficult? One meter, about 40 inches Human hair, about 100 microns Wavelength of light, about 1 micron LIGO sensitivity, 10 -18 meter Nuclear diameter, 10 -15 meter Atomic diameter, 10 -10 meter Earthtides, about 100 microns Microseismic motion, about 1 micron Precision required to lock, about 10 -10 meter

45. LIGO-G010398-00-M Laser stabilization IO 10-Watt Laser PSL Interferometer 15m 4 km TidalWideband  Deliver pre-stabilized laser light to the 15-m mode cleaner Frequency fluctuations In-band power fluctuations Power fluctuations at 25 MHz  Provide actuator inputs for further stabilization Wideband Tidal 10 -1 Hz/Hz 1/2 10 -4 Hz/ Hz 1/2 10 -7 Hz/ Hz 1/2

46. LIGO-G010398-00-M Prestabalized Laser performance  > 18,000 hours continuous operation  Frequency and lock very robust  TEM 00 power > 8 watts  Non-TEM 00 power < 10%

47. LIGO-G010398-00-M LIGO “first lock” signal Laser X Arm Y Arm Composite Video

48. LIGO-G010398-00-M Watching the Interferometer Lock signal X Arm Y Arm Laser X arm Anti-symmetric port Y arm Reflected light 2 min

49. LIGO-G010398-00-M Lock Acquisition

50. LIGO-G010398-00-M 2km Fabry-Perot cavity 15 minute locked stretch

51. LIGO-G010398-00-M Detecting the Earth Tides Sun and Moon

52. LIGO-G010398-00-M Astrophysical Signatures data analysis  Compact binary inspiral: “chirps” »NS-NS waveforms are well described »BH-BH need better waveforms »search technique: matched templates  Supernovae / GRBs: “bursts” »burst signals in coincidence with signals in electromagnetic radiation »prompt alarm (~ one hour) with neutrino detectors  Pulsars in our galaxy: “periodic” »search for observed neutron stars (frequency, doppler shift) »all sky search (computing challenge) »r-modes  Cosmological Signals“stochastic background”

53. LIGO-G010398-00-M “Chirp Signal” binary inspiral distance from the earth r masses of the two bodies orbital eccentricity e and orbital inclination i determine

54. LIGO-G010398-00-M Binary Inspirals signatures and sensitivity Compact binary mergers LIGO sensitivity to coalescing binaries

55. LIGO-G010398-00-M Signals in Coincidence Hanford Observatory Livingston Observatory

56. LIGO-G010398-00-M Detection Strategy coincidences  Two Sites - Three Interferometers »Single Interferometernon-gaussian level~50/hr »Hanford (Doubles) correlated rate (x1000)~1/day »Hanford + Livingston uncorrelated (x5000)<0.1/yr  Data Recording (time series) »gravitational wave signal (0.2 MB/sec) »total data (16 MB/s) »on-line filters, diagnostics, data compression »off line data analysis, archive etc  Signal Extraction »signal from noise (vetoes, noise analysis) »templates, wavelets, etc

57. LIGO-G010398-00-M Interferometer Data 40 m prototype Real interferometer data is UGLY!!! (Gliches - known and unknown) LOCKING RINGING NORMAL ROCKING

58. LIGO-G010398-00-M The Problem How much does real data degrade complicate the data analysis and degrade the sensitivity ?? Test with real data by setting an upper limit on galactic neutron star inspiral rate using 40 m data

59. LIGO-G010398-00-M “Clean up” data stream Effect of removing sinusoidal artifacts using multi-taper methods Non stationary noise Non gaussian tails

60. LIGO-G010398-00-M Inspiral ‘Chirp’ Signal Template Waveforms “matched filtering” 687 filters 44.8 hrs of data 39.9 hrs arms locked 25.0 hrs good data sensitivity to our galaxy h ~ 3.5 10 -19 mHz -1/2 expected rate ~10 -6 /yr

61. LIGO-G010398-00-M Detection Efficiency Simulated inspiral events provide end to end test of analysis and simulation code for reconstruction efficiency Errors in distance measurements from presence of noise are consistent with SNR fluctuations

62. LIGO-G010398-00-M Setting a limit Upper limit on event rate can be determined from SNR of ‘loudest’ event Limit on rate: R < 0.5/hour with 90% CL  = 0.33 = detection efficiency An ideal detector would set a limit: R < 0.16/hour

63. LIGO-G010398-00-M gravitational waves ’s light “Burst Signal” supernova

64. LIGO-G010398-00-M Supernovae gravitational waves Non axisymmetric collapse ‘burst’ signal Rate 1/50 yr - our galaxy 3/yr - Virgo cluster

65. LIGO-G010398-00-M pulsar proper motions Velocities -  young SNR(pulsars?)  > 500 km/sec Burrows et al  recoil velocity of matter and neutrinos Supernovae asymmetric collapse?

66. LIGO-G010398-00-M Supernovae signatures and sensitivity

67. LIGO-G010398-00-M “Periodic Signals” pulsars sensitivity  Pulsars in our galaxy »non axisymmetric: 10-4 <  < 10-6 »science: neutron star precession; interiors »narrow band searches best

68. LIGO-G010398-00-M “Stochastic Background” cosmological signals ‘Murmurs’ from the Big Bang signals from the early universe Cosmic microwave background

69. LIGO-G010398-00-M LIGO conclusions  LIGO construction complete  LIGO commissioning and testing ‘on track’  “First Lock” officially established 20 Oct 00  Engineering test runs begin now, during period when emphasis is on commissioning, detector sensitivity and reliability  First Science Run will begin during 2003  Significant improvements in sensitivity anticipated to begin about 2006